Hi,
I worked in the UK as an osteopath until we left for Germany late last year (and plan to again once my language skills are up-to-scratch) and I have had conversations about this topic with many patients over the years.
If you’re getting pain while you sit then you are sitting in a way that is stressing your body. This is usually because we put the low back flat against the chair which is in effect the same movement as bending forwards if you were standing. At a spinal level, those movements are the same.
Your low back muscles are therefore held on stretch and working to prevent a further falling forward and any muscle that continually works hard squeezes out its blood supply (just as a squeezed sponge holds less water). This sets up the conditions for pain.
It’s important to try to move as regularly as you can, at least every 20 minutes., even if all you do is stand, stretch out and sit down. But I know what’s it like when you’re working on a composition or to a deadline, it’s hard to break away.
Buy a decent chair that can be adjusted in many different ways (Ikea used to have a good one for about £250) but learn to sit on it well. Keep the curve in the lower back which means feet flat on floor and the bones on the front of the hip pointing slightly down (that’s a difficult instruction without a demonstration). A triangular cushion, or chair where the front can be lower than the back can help this.
You don’t need an expensive chair, they are a triumph of marketing over evidence. It matters more how you sit on it and that you move as often as you can. A rolled up towel can be sufficient as a lumbar support and a good way to keep the curve in the lower back. A more beneficial sitting posture should not feel tight.
I would recommend finding a local osteopath or physiotherapist to give you a proper assessment. They will screen you for the more sinister, but thankfully, rare, forms of back pain and if they’re good, explain their findings and give you a plan for what to do.
Richard